The present invention relates to retaining works made in ground, and in particular to works that are to form the walls of wharves.
More particularly, the invention relates to a retaining work in ground having a front portion extending substantially vertically while separating a first portion of ground from a second portion of ground.
The invention is particularly advantageous when the levels of the first and second portions of ground are substantially different, e.g. when the difference in height between the first and second portions of ground is of the order of 15 meters (m) to 30 m.
This applies when the first portion of ground is situated under a body of water, the front portion of the retaining work then constituting a wharf wall also separating the body of water from the second portion of ground.
Traditionally, the front portion of such a retaining work is a plane wall, and part of the forces exerted by the second portion of ground on the front portion are taken up by elongate metal ties connecting the plane wall to a rear anchor curtain that is parallel to the plane wall and that is situated in the second portion of ground at a distance from the plane wall, thereby stabilizing the work. The rear anchor curtain may be situated at more than 50 m from the plane wall, and the metal ties may be positioned at a depth of about 5 m. Conventionally, work begins by making the plane wall and the anchor curtain in the second portion of ground. Thereafter, the volume of ground that extends over the distance between the plane wall and the rear curtain is dug out to the depth at which the metal ties are to be positioned.
It can thus be understood that the volume of ground that needs to be dug out in order to be able to put the metal ties into place is very large, particularly since the plane wall is of great length. Furthermore, after the metal ties have been put into place, it is necessary to put back the volume of ground that was previously dug out. In general, underground water is present, and its level needs to be lowered while the work is taking place.
Those successive operations of lowering the underground water and of moving earth, which require very large volumes of earth to be moved, are particularly lengthy, tedious, and expensive.